The technology described herein relates generally to gas turbine engines, and more particularly, to methods for repairing combustor liners used with gas turbine engines.
A gas turbine engine includes a compressor for compressing air which is mixed with a fuel and channeled to a combustor wherein the mixture is ignited within a combustion chamber for generating hot combustion gases. At least some known combustors include a dome assembly, a cowling, and liners to channel the combustion gases to a turbine, which extracts energy from the combustion gases for powering the compressor, as well as producing useful work to propel an aircraft in flight or to power a load, such as an electrical generator. The liners are coupled to the dome assembly with the cowling, and extend downstream from the cowling to define the combustion chamber.
At least some known liners include a plurality of panels that are connected together with riveted, bolted, or welded connections. A portion of the panels include cooling nuggets formed between adjacent panels that extend radially outwardly from the panels and away from the combustion chamber. Accordingly, such cooling nuggets are not subjected to the same degree of heat as portions of the panels adjacent the combustion chamber, and as such, during operation thermal stresses may be induced within the panels. Over time, continued operation with thermal stresses may cause panels to thermally fatigue, causing weakening and/or cracking to develop within the panels.
Current repair methods include welding thermal fatigue cracks. Additionally, patches may be attached to areas of panels that are weakened by thermal stresses. However, if the thermal stresses have induced thermal fatigue or distress in larger areas of the panels or in a plurality of panels, the combustor may not have enough structural integrity within such panels to enable patches to be attached. The location of openings in the panels, such as cooling or dilution holes, and the use of thermal barrier coatings add additional complexity to the use of welds and patches. In such cases, repair of such panels is not a feasible option, and instead the entire combustor liner is replaced.
Because the liner is coupled to the cowl and the dome assembly, often the entire combustor must be disassembled for the liner to be replaced. Furthermore, when the fasteners are removed from the cowl and dome assembly, precise dimensional relations between the components may be altered and as a result, special tooling may be required during re-assembly. Thus, replacing a combustor liner including cooling nuggets may be a time-consuming and expensive process.